gitcvs-migration(7) Manual Page

NAME

gitcvs-migration -
git for CVS users

SYNOPSIS

git cvsimport *

DESCRIPTION

Git differs from CVS in that every working tree contains a repository with
a full copy of the project history, and no repository is inherently more
important than any other. However, you can emulate the CVS model by
designating a single shared repository which people can synchronize with;
this document explains how to do that.

Developing against a shared repository

Suppose a shared repository is set up in /pub/repo.git on the host
foo.com. Then as an individual committer you can clone the shared
repository over ssh with:

$ git clone foo.com:/pub/repo.git/ my-project
$ cd my-project

and hack away. The equivalent of cvs update is

$ git pull origin

which merges in any work that others might have done since the clone
operation. If there are uncommitted changes in your working tree, commit
them first before running git pull.

Note

The pull command knows where to get updates from because of certain
configuration variables that were set by the first git-clone
command; see git config -l and the git-config(1) man
page for details.

You can update the shared repository with your changes by first committing
your changes, and then using the git-push command:

$ git push origin master

to "push" those commits to the shared repository. If someone else has
updated the repository more recently, git-push, like cvs commit, will
complain, in which case you must pull any changes before attempting the
push again.

In the git-push command above we specify the name of the remote branch
to update (master). If we leave that out, git-push tries to update
any branches in the remote repository that have the same name as a branch
in the local repository. So the last push can be done with either of:

$ git push origin
$ git push foo.com:/pub/project.git/

as long as the shared repository does not have any branches
other than master.

Setting Up a Shared Repository

We assume you have already created a git repository for your project,
possibly created from scratch or from a tarball (see
gittutorial(7)), or imported from an already existing CVS
repository (see the next section).

Assume your existing repo is at /home/alice/myproject. Create a new "bare"
repository (a repository without a working tree) and fetch your project into
it:

Next, give every team member read/write access to this repository. One
easy way to do this is to give all the team members ssh access to the
machine where the repository is hosted. If you don’t want to give them a
full shell on the machine, there is a restricted shell which only allows
users to do git pushes and pulls; see git-shell(1).

Put all the committers in the same group, and make the repository
writable by that group:

$ chgrp -R $group /pub/my-repo.git

Make sure committers have a umask of at most 027, so that the directories
they create are writable and searchable by other group members.

Importing a CVS archive

First, install version 2.1 or higher of cvsps from
http://www.cobite.com/cvsps/ and make
sure it is in your path. Then cd to a checked out CVS working directory
of the project you are interested in and run git-cvsimport:

$ git cvsimport -C <destination> <module>

This puts a git archive of the named CVS module in the directory
<destination>, which will be created if necessary.

The import checks out from CVS every revision of every file. Reportedly
cvsimport can average some twenty revisions per second, so for a
medium-sized project this should not take more than a couple of minutes.
Larger projects or remote repositories may take longer.

The main trunk is stored in the git branch named origin, and additional
CVS branches are stored in git branches with the same names. The most
recent version of the main trunk is also left checked out on the master
branch, so you can start adding your own changes right away.

The import is incremental, so if you call it again next month it will
fetch any CVS updates that have been made in the meantime. For this to
work, you must not modify the imported branches; instead, create new
branches for your own changes, and merge in the imported branches as
necessary.

If you want a shared repository, you will need to make a bare clone
of the imported directory, as described above. Then treat the imported
directory as another development clone for purposes of merging
incremental imports.

Advanced Shared Repository Management

Git allows you to specify scripts called "hooks" to be run at certain
points. You can use these, for example, to send all commits to the shared
repository to a mailing list. See githooks(5).

Providing CVS Access to a git Repository

It is also possible to provide true CVS access to a git repository, so
that developers can still use CVS; see git-cvsserver(1) for
details.

Alternative Development Models

CVS users are accustomed to giving a group of developers commit access to
a common repository. As we’ve seen, this is also possible with git.
However, the distributed nature of git allows other development models,
and you may want to first consider whether one of them might be a better
fit for your project.

For example, you can choose a single person to maintain the project’s
primary public repository. Other developers then clone this repository
and each work in their own clone. When they have a series of changes that
they’re happy with, they ask the maintainer to pull from the branch
containing the changes. The maintainer reviews their changes and pulls
them into the primary repository, which other developers pull from as
necessary to stay coordinated. The Linux kernel and other projects use
variants of this model.

With a small group, developers may just pull changes from each other’s
repositories without the need for a central maintainer.